An Important Medical Need: Effective Circulatory System Access.
More than eighty percent (80%) of dialysis patients in the United States (e.g., those suffering from end stage renal disease (i.e., kidney failure)) undergo regular hemodialysis treatments.
In order for these treatments to be performed, these patients need an effective blood or circulatory system access, an entry mechanism which allows the blood in the body to be easily taken from an artery or vein (so that it may then be circulated through the dialysis machine) and then be returned to the body through a vein.
The instant invention, as shown in FIG. 1, relates to a novel design for such an access.
Many times, patient access is needed for dialysis treatments as often as thrice weekly. There are two primary blood accesses: permanent and temporary. Permanent accesses are designed to stay in the body for longer periods of time. Temporary accesses are in the body for a short amount of time.
Overview of Current Modes of Access.
Two common types of permanent accesses are:                1. AV Graft        2. AV FistulaThe acronym “AV” refers to “arteriovenous,” referring to the arteries and veins in the human body.        
Referring, now, to FIG. 2, an AV graft construction is depicted. An AV graft connects an artery to a vein under the skin by means of an artificial blood vessel. These constructions are commonly used when the patient's own blood vessels are too small or weak for fistula construction (an alternative access mechanism discussed below). Often, these patients are elderly or have pre-existing diabetes mellitus.
AV grafts, which are most commonly placed in the upper arm, lower arm, and/or thigh, comprise a conduit which is either straight or U-shaped. The graft is placed close to the surface of the skin for easier needle insertion.
The graft may be made from a leg vein or cow (i.e., bovine) vein; it may also be made from a variety of artificial or synthetic (i.e., man-made) materials, such as polytetrafluoroethylene. Some synthetic constructions are known by their brand names (e.g., Gortex, Impra).
After the graft is placed, two to four weeks should pass before the graft is punctured to allow adequate healing and sufficient growth of tissue to stabilize the graft.
Referring, now, to FIG. 3, an AV fistula is depicted. An AV fistula is a close connection made directly between an artery and vein. The artery and vein are joined together under the skin.
The AV fistula is created internally, and it is used for prolonged periods of time. Its construction involves a small operation to directly join an artery and vein, allowing arterial blood to flow directly into the vein. According to information presented during a symposium at the University of Cincinnati Medical Center (i.e., “Angio Access for Dialysis”), an AV fistula usually lasts longer and usually has fewer problems than does a synthetic graft (like Gortex).
Blood vessels of the arm are usually chosen (e.g., at the wrist or upper forearm). Due to arterial pressure, the vein will subsequently increase in size and its walls will thicken. Once the vein has had time to heal, it is easier to put a needle into the vein, so that the blood will flow through the dialyzer by means of the blood pump on the machine.
The amount of time after construction/placement before an access may be used depends upon the type of access. Fistula maturation generally requires three to four months (so that the vein has time to heal, enlarge, and support sufficient blood flow for use in hemodialysis).
The typical locations for hemodialysis access are:                1. Arm: Right or left, upper or lower; and        2. Leg: Right or left, upper or lower.        
Problems Associated with Current Access Methods
Although the accesses just described are highly effective, and constitute a critical “life line” for the patient, they, like many other biological systems, are somewhat fragile, and both types of accesses feature potential dangers.
For example, accesses must be carefully managed because, typically, they are punctured (not uncommonly twice) for each treatment.
One of the most important things to do, therefore, is to rotate needle stick placement sites. Changing the stick sites for each dialysis treatment allows the body to have the time necessary for healing of those localized sites to occur. In the case of a routine cannulation, for example, healing occurs fairly rapidly, so site rotation is a convenient and effective method of ensuring healthy access sites; however, if a laceration and/or infiltration of the stick site has occurred, it can take as long as two to six weeks for healing of a stick site to occur.
Thus, in a nutshell, healing time is important. Like your skin, your artery-vein graft needs time to recover from repeated needle sticks. If the site is not rested, it will become weak, resulting in a weak region in the access called an aneurysm. Rotating needle stick sites helps keep an access strong.
Another important current practice involves access immobilization during treatment.
Many lay observers are surprised to learn that one of the greatest possible dangers to the integrity of a patient's access site is the possible laceration and/or infiltration of the AV graft or fistula by the sharp point of the needle. This type of damage can be serious; not uncommonly, it requires the patient to visit a vascular surgeon for repair or replacement.
As a consequence, the current state of the art in treatment recognizes that needles should be taped securely to keep them from moving and causing damage to the access during the dialysis. Thus, once the patient has been cannulated (i.e., punctured with the needle), the needle is then taped in place securely to help minimize movement. The patient is further instructed to remain as still as possible for the duration of the treatment.
Most patients do a fine job of remaining fairly immobile during treatment, but there are naturally times when an involuntary movement may cause the patient's access site to move. During movement, the potential for inadvertent damage is substantially increased. And this damage can occur at the beginning of the hemodialysis treatment (during insertion of the needle), during the treatment itself, or it can even occur after the completion of hemodialysis treatment (during the removal of the needle).
A Critical Need: a Safer Form of Access.
What is needed, in the field of hemodialysis treatments and, indeed, in any fluid/medication-delivery applications such as intravenous cannulation, is a way to utilize the sharp puncture point of the needle in order to gain access during cannulation but to simultaneously minimize the potential of the same sharp needle further puncturing the region after cannulation (i.e., during and at the close of treatment).